Layman, HT receivers are internally complex eventhough some have plug in modules, the majority of them have quite of few wires soldered onto terminals and unless you have the proper soldering equipment it will be not easy to replace. In my opinion you can forget about fixing your own receiver, unless you have a good experience in troubleshooting these things plus a good dose of HT repairing technics.
If you're getting a sort of crakling sound in the speakers that doesn't go away or gradually get worse as the receiver stays on for a while, there is a good possibility (and it's a very common problem) that your receiver has some leaky sound output IC (integrated circuits) and preamp transistors or chips depending on your receiver causing crackling into your speakers.
Problems like that are easily detected by spraying some aerosol freon (which we call it Freez it) out of a spray can wright on top of the faulty component and if the crackling disappears, you know the component is internally leaky and should be replaced.
I am just speculating that your problem is what I had mentioned above, it could very well be of a different nature, but if you could be a little more specific, we might be able to help you better.
